The present invention relates to an optical reader comprising optical fiber bundles.
Optical readers comprising optical fibers are becoming increasingly popular in the art. These readers detect the presence or absence of a mark in a predetermined area of a document in sheet form and are used in facsimile systems, card processors, etc. More specifically, light is conveyed from a light source to the area on the sheet by means of one or more illuminating optical fibers. Light reflected from the area is conveyed to a light sensor such as a photosensitive diode or transistor through one or more reading optical fibers. The ends of the fibers facing the sheet are placed in close proximity.
When a mark is present in the area, the amount of light which reaches the light sensor is less than when the mark is not present so that the light sensor detects the presence or absence of the mark in the form of two discrete light levels respectively.
Whereas these prior art optical readers are generally capable of reliably detecting marks made by a non-glossy writing means such as a felt-tip pen, erroneous readings often occur when the marks are made by a glossy marking means such as a pencil. Depending on the angles of orientation of the ends of the optical fibers, more light might actually be conveyed to the light sensor from the glossy surface of a pencil mark than from the white background of the sheet. Although considereble experimentation has been performed especially regarding the orientation of the ends of the optical fibers, there has not been achieved heretofore an optical reader utilizing optical fibers which can detect the presence of marks made by both non-glossy and glossy marking means with complete reliability.